On Sat, 2007-12-22 at 04:31 -0800, Arjan van de Ven wrote: > Hi, > > Linus really wants the extended (4Kb) PCI configuration space (using MCFG > acpi table etc) to be opt-in, since there's many issues with it and most > drivers don't even use/need it. The idea behind opt-in is that if you don't > use it, you don't get to suffer the bugs... > > Booted on my 64 bit test machine; sadly it has a defunct BIOS that doesn't > have a working MCFG. > > > From: Arjan van de Ven <[EMAIL PROTECTED]> > Subject: Make MMCONFIG space a driver opt-in > > There are many issues with using the extended PCI configuration space > (CPU, Chipset and most of all BIOS bugs). This while the vast majority of > drivers > and devices don't even use/need to use the memory mapped access methods since > they > don't use the config space beyond the traditional 256 bytes. > > This patch makes accessing the extended config space a driver choice, via the > > pci_enable_ext_config(pdev) > > API function; drivers that want/need the extended configuration space should > call this. > (a separate patch will be posted to add this function call to the driver that > uses this)
That doesn't look like the right approach to me. The extended config space is generally used by PCI capabilities. So you end up in a situation where part of the capabilities will be invisible until somebody calls your new API, which might affect generic code in some cases beyond simply what a driver is supposed to do. I think best is to have your low level config ops switch between indirect and MM depending on the requested register offset. Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
